Got a compression tester...
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  1. #1
    PWCToday Newbie
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    Got a compression tester...

    I have two 1995 Waveraider 700's. They both ran great but one smoked more than the other. The one that smoked started running rough and wouldn't go over 3000 RPM. One day I added some SeaFoam to the fuel to see if there was maybe some water in the mix. When I unscrewed the gas cap it was under pressure and popped off into my hand. It ran great for about 5 seconds after that then went right back to running rough. It was suggested that maybe the gas tank vent was plugged and sure enough, the line had a kink in it. Cut the kink out and unfortunately made no difference.

    So... I bought a compression tester (as suggested in the first place) and ran a test today. The back cylinder was 120lbs as I expected due to it's age but the front cylinder was 95lbs. This seems like a big difference. Am I in need of rebuild? I have the feeling that since it ran bad, then ran good, then back to bad that it was a carb issue. But the difference in cylinders and significantly low compression in the one may suggest otherwise.

    What to do? Is this acceptable or is there no way it's going to run will with a cylinder that low? What's next?

  2. #2
    Frequent Poster Dave in DE's Avatar
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    Re: Got a compression tester...

    Ya, that's far more than 10%. You'll need to rebuild at least the top end. I would rebuild the carb also if it's been awhile sense last time.
    Last edited by Dave in DE; 08-09-2019 at 10:43 PM.

  3. #3
    PWCToday Newbie
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    Re: Got a compression tester...

    In my world a top end is just heads and valves. From looking at kits I'm assuming pistons are considered part of the top end also. I intend to tear it apart before ordering any parts just so that I know exactly what's going on and what will need replaced. Quick question; does the carb or fuel delivery system affect compression in these 2 strokes any? The more I read up on them the less clear it seems to be to me.

  4. #4
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: Got a compression tester...

    Yes, tear it down before ordering anything. A lower rod or crank bearing crapping out will also do what you describe. It can feel like water in the gas or one cylinder dropping out as the bearing frees then tries locking back up meanwhile spitting metal debris up into the cylinders and ruining the top end as well.
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  5. #5
    Frequent Poster Dave in DE's Avatar
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    Re: Got a compression tester...

    Quote Originally Posted by Catscratch View Post
    In my world a top end is just heads and valves. From looking at kits I'm assuming pistons are considered part of the top end also. I intend to tear it apart before ordering any parts just so that I know exactly what's going on and what will need replaced. Quick question; does the carb or fuel delivery system affect compression in these 2 strokes any? The more I read up on them the less clear it seems to be to me.
    In the 2stroke world a top end rebuild is cyl's, pistons, rings, basically. Myself is correct you'll won't to check out the crank/rod brgs while the top is off.

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